1. Field of the Invention
This invention relates to an illuminated display device for road traffic, wherein a plurality of display points with display lenses, which have a light inlet surface and a light outlet surface and are illuminated from a direction of a back of the display surface by respectively associated illumination elements of lesser diameter, are formed in or on a display surface, and wherein a light inlet surface and/or a light outlet surface each is shaped so that the light intensity distribution on the display side has a greater extension in the horizontal direction than in the vertical direction.
2. Description of Related Art
An illuminated display device of this type is disclosed in U.S. Pat. No. 4,113,347. In this known illuminated display device a lateral increase of the angle of radiation, or respectively of the light intensity distribution is achieved with two lens elements embodied next to each other.
Japanese Patent Reference JP-A 03 054 592 discloses arranging the cylinder axes of two cylindrical lenses of different curvatures perpendicularly with respect to each other for achieving a greater extension of the light intensity distribution in one direction over the other.
A further illuminated display device is disclosed by German Patent Reference DE 40 40 467 C1. In this known illuminated display device a plurality of display points are formed on a display surface by respective display lenses, which are illuminated from a back of the display surface by illuminating elements in the form of optical fibers directed on the display lenses. Display points with relatively large surfaces, which improve the visibility of a displayed character, are achieved with the display lenses, whose diameter is greater than the diameter of the optical fibers. In order to achieve a sufficiently high illumination density, the light emission is bundled with the lenses, but it is possible for the illumination density to become too low for good visibility at greater angles outside of the radiating axis, in particular in case of lighter surroundings.
One object of this invention is to provide an illuminated display device of the type mentioned above, wherein an increased illumination density of the light points at increased observation angles is achieved, while the light output of the illuminating elements remains unchanged, wherein the embodiment is also advantageous for maintenance purposes.
This object is achieved with a light outlet surface and/or a light inlet surface formed so that the light intensity distribution on the display side is greater in the horizontal direction than in the vertical direction. An increased light intensity or illumination density of the display points under increased horizontal observation angles results from this design of the display lenses, so that the visibility of the display is assured, even when approached from a curve in the road, for example. Although the distribution of the light intensity in the vertical direction is reduced to a correspondingly lesser angle with respect to the radiating axis at the expense of the light intensity distribution in the horizontal direction, it is sufficient for achieving requirements for good readability from the customary observation distances. The light from the display as a whole is considerably improved for actual observation conditions in road traffic.
The further measures are also particularly advantageous for maintenance because the display lens has a cylindrical section adjoining the light inlet surface, and on its radially symmetrical light inlet surface tapers toward an exterior in the form of a section of a cone, and has a central concave section. It is sufficient if the display lens is designed radially symmetrical at least in the light inlet area.
A suitable embodiment of the illuminated display device for good visibility consists in that the half-width value of the light intensity distribution in the horizontal direction is greater by at least a factor of 1.4 than the half-width value in the vertical direction. For example, the half-width value in the horizontal direction can be twice as great as in the vertical direction, whereas within the half-width value the light intensities with the same light sources is just as great as within the half-width value of light intensity distributions of customary radially symmetrical light intensity distributions. If up to now the half-width value of a radially symmetrical light intensity distribution was 12xc2x0, for example, this light intensity distribution is achieved with the present display device within a vertical half-width value of 6xc2x0, for example, and a horizontal half-width value of 24xc2x0, so that doubling of the corresponding extra-axial recognition angle results in the important horizontal range.
One embodiment of the display lenses has a radius of curvature of the light outlet surface which is less in the horizontal direction than in the vertical direction, wherein in another embodiment the light outlet surface is curved convexly toward the outside in the vertical direction and has a curvature radius of zero in the horizontal direction.
For production and mounting, the display lenses is designed so that the light outlet surface is formed in the shape of a section of a cylinder. Because of the cylindrical shape it is possible, for example, to produce the lenses from a glass rod made of an acrylic material and to insert a cylindrical piece into a corresponding bore in the display surface and fix it in place there.
A defined positioning and contact, as well as a tight securing possibility against the display surface, is achieved because the display lens has a flange-like collar on the circumference which rests on the outside of the display surface.
One step is advantageous for simple positioning of the display lenses in the circumferential direction, wherein a marker for the installed position is formed on the collar, In this case, a simple positioning aid includes the marker designed as a section of a circle.
With the above embodiments it is also possible to exchange the inlet surface with the outlet surface by rotating the lens by 180xc2x0.